1. Technical Field of the Invention
The present invention relates to blood controls and more particularly to controls for use in indirect acute phase protein measurement tests.
2. Background
There are various methods that have been described which result in the indirect measurement of the acute-phase (inflammatory response) proteins, including the erythrocyte sedimentation rate (ESR) test, the Zeta Sedimentation Ratio Test, and Plasma Viscosity Test. See Bull, B., Brailsford, D. The Zeta Sedimentation Ratio. Blood. 1972; 40: 550-559. Harkness, J. A New Instrument for the Measurement of Plasma Viscosity. Lancet. 1963; 280-281.
By way of the history, possibly the first detailed method for indirectly measuring (by erythrocyte sedimentation) acute-phase proteins was described by Fahraeus in 1921. Fahraeus, Robin. Acta Medica Scandinavica. 1921; 55:1-228. The test was later modified by Fahraeus and Westergren. Westergren, A. Studies of the Suspension Stability of the Blood in Pulmonary Tuberculosis. Acta Medica Scandinavica. 1921;54:247-282. Although there have been many modifications of this manual test, the basic method has survived. The method involves diluting blood, filling a standardized tube, and measuring the distance the red cells settle in a specific time interval.
The erythrocyte sedimentation rate test (ESR) measures the proteins of blood that are increased by inflammation. The presence of these proteins causes an increase in viscosity and also causes the red cells to sediment more rapidly. The mechanisms for the changes in these proteins are better understood today than when the test was introduced by Fahraeus in 1921. Fahraeus, Robin. Acta Medica Scandinavica. 1921; 55: 1-228 (page 121). However, he recognized the importance of fibrinogen and globulins which are the major proteins producing an increased ESR.
It is believed that the basis for the increased sedimentation is due to a group of proteins called acute phase proteins. These are macromolecules of the plasma such as fibrinogen and the globulins. The proteins are synthesized in the liver and their levels in the plasma rise with inflammation. Kushner, I. The Phenomenon of the Acute Phase Response. Ann N.Y. Acad. Sci. 1982; 389: 39-48. Han Moshage divides the acute phase proteins into two groups: (1) Type I proteins, which include serum amyloid, C-reactive protein, Complement C3, haptoglobin and .alpha.1-acid glycoprotein. These are induced by interleukin-1-like cytokines such as IL-1.alpha., IL-1B, TNF-.alpha., and TNF-B; and (2) Type II proteins, which are induced by IL-6 like cytokines which include IL-61, LIF, IL-II, OSM, CNTF, and CT-1. The IL-6 will synergize with IL-1 to induce the Type I proteins of the cytokines. IL-6 is believed to be the main cause of the induction of acute-phase proteins. Gabay, Cem et al. Acute-Phase Proteins and Other Systemic Responses to Inflammation. The New England Journal of Medicine. 448-454. Moshage, Han. Cytokines and the Hepatic Acute Phase Response. Journal of Pathology. 1997; 181:257-266.
Coulter Corporation has offered an instrument, the ZETAFUGE, for determining the zeta sedimentation ratio. Bull and Brailsford (Bull, B., Brailsford, D. The Zeta Sedimentation Ratio. Blood 1972; 40; 550-559) have described a method for making controls or "standards" for this system.
The plasma viscosity test is commonly employed for indirectly measuring acute phase proteins in the United Kingdom. One suitable instrument, the Viscometer, and controls for it are manufactured by Coulter Corporation. This technique was described by Cooke and Stuart in 1988. An earlier article describing this methodology was published in the J. Clinical Pathology in 1980 by Stuart and Kenny. Cooke, B. M. et al. Automated Measurement of Plasma Viscosity by Capillary Viscomenter. J. Clin Pathol. 1988; 41:1213-1216. Stuart, J., Kenny, M. W. Blood Rheology. J. Clin Path. 1980; 33:417-429.
Other automated instruments have appeared on the market. Examples include the Ves-Matic.RTM., Mini-Ves.RTM., Sed-Mat.RTM., and ESR-8/Sedimatic 8.TM..
Methods for determining acute phase proteins can be influenced by numerous factors. Several of these relate to the type of tube used and other environmental conditions. For instance, bench-top vibration, temperature and tube angle may affect rates obtained. The need for using control preparations for these methods is well established. The ICSH Committee has addressed this issue in 1988 (International Committee for Standardization in Haematoloy (Expert panel on Blood Rheology). Guidelines on Selection of Laboratory Tests for Monitoring the Acute Phase Response. J. Clin Pathol. 1988, 41; 1203-1212) and 1993 (Thomas, Robert et al. Calibration and Validation for Erythrocyte Sedimentation Tests. Arch Pathol Lab Med. 1993; 117; 719-723). They describe the use of selected blood specimens for quality controlling the "routine" ESR method by comparison to the "reference" method. One control for use in a particular ESR test is that addressed in U.S. Pat. Nos. 5,863,799 and 5,888,822. The Clinical Laboratory Improvement Act (CLIA-88) mandated that control preparations be used for all automated instruments. See e.g., 42 C.F.R., Part 493, Subpart K (12), incorporated by reference herein. Prior to CLIA-88, the use of controls was not mandated.
From the above it is clear that the concept of using control preparations for monitoring all three methods has been well known. Unmodified human blood can provide controls which have limited stability. In those instances, the controls are used in applications where the stability that is desired is less than several months.